"Such an amazing rewrite of history since 1962 and 1990. Newt, I thought you, of all people, a historian, would be true to who this guy really was," one said. And another wrote: "This clenched-fist, murdering guerilla warrior does not deserve respect from informed Americans."

Gingrich said he was "very surprised" by reactions. And in response to the uproar, he wrote his Friday newsletter asking his followers what they would have done about Mandela's views and apartheid in South Africa.

Sen. Ted Cruz (R-Texas) faced similar backlash on comments he made lauding Mandela's life and career. When Crowley asked if the criticism of their comments comes from fellow conservatives, Gingrich said they are people who "bought a rationale that defined everybody who was in anyway in rebellion against the established system in the third world as anti-American."

Crowley also asked Gingrich if former President Ronald Reagan and former Prime Minister Margaret Thatcher were on the right side of history in opposing sanctions on South Africa for its apartheid government. And Gingrich said they were.

"In all fairness to Reagan...," Gingrich said. "Reagan's ambassador to South Africa consistently put pressure on the government to modify its position and consistently condemned apartheid. But their commitment was to defeat the Soviet empire."